This invention relates to an apparatus for poling a piezoelectric ceramic, more particularly to an apparatus for poling a piezoelectric ceramic which has two spaced electrodes, wherein the piezoelectric ceramic to be poled is placed on one of said two electrodes and spaced away from the other one of said two electrodes.
It is known that the piezoelectric electric effect of a ceramic material may be provided by poling said ceramic material. Referring to FIG. 1, a conventional apparatus for poling a piezoelectric ceramic includes a poling tank 90 in which the silicon oil 91 is contained. A piezoelectric ceramic disc 92 is dipped in said silicon oil 91. Two sides of said piezoelectric ceramic disc 92 are electroplated by a layer of silver 93, and the disc 92 is placed on a metal plate 94. The upper layer of silver 93 and the metal plate 94 are respectively connected to the positive and negative electrodes of a DC power supply 95 so as to apply a given voltage to the piezoelectric ceramic disc 92. In this way, the piezoelectric ceramic disc can be poled in a poling field resulting from said given voltage and a suitable temperature of the silicon oil 91 in the poling tank 90. However, since the upper layer of silver 93 is connected to the positive electrode of the DC power supply 95 via the contact of a probe 96, said upper layer 93 silver is liable to be scraped off from said piezoelectric ceramic disc 92 by said probe 96. In addition, when the voltage applied to the piezoelectric ceramic disc 92 is high and unstable, said piezoelectric ceramic disc 92 will be damaged or broken due to the ripple caused by said high voltage from said DC power supply 95. This will lower the production yield of the poled piezoelectric ceramic disc. Moreover, by using said conventional apparatus for poling a piezoelectric ceramic disc, it is necessary to pay attention to the poling time of the piezoelectric ceramic disc during the poling process and replace the piezoelectric ceramic disc which has been poled with a disc which has not been poled at the end of the poling process. These procedures are messy and involve high labor-costs. Moreover, the piezoelectric ceramic disc is liable to be damaged during said replacement process. Therefore, such a conventional poling apparatus is not suited for use in a fully automated industry which requires mass production of piezoelectric ceramics.